In U.S. Pat. No. 3,632,145, a trailer hitch head or fifth wheel is disclosed including a locking member which engages a pair of jaws to hold the jaws in closed position engaging the kingpin of a trailer. The locking member is manually movable against the bias of a stiff spring to an open jaw position to allow entry or exit of the kingpin from the jaws. In open position vertically movable keepers biased to an engaged position with the locking member hold the locking member in open position so that the operator can drive the trailer into or out of the hitch.
However, this construction requires that the locking member be manually moved to the open position until the vertically movable keepers are released to hold the locking member in open position.
In U.S. Pat. No. 3,892,426 a one-way gate for a trailer hitch head or fifth wheel is disclosed. However, in this construction, the one-way gate must be manually moved to open position which allows the kingpin to exit.